1. rushing up to the tail end of slower moving traffic ahead
2. overtakes taking forever where the speed differential is minimal
3. boxing-in another vehicle when there is little or no speed differential
4. tap dancing on the brake pedal for no apparent reason when the driver wakes up
5. cutting across lanes late to get to an exit slip road
6. middle lane blocking on 3 or 4 lane roads
7. unauthorised speed limiting by cruising in lane 2 of 2 - particularly common amongst Cambridgeshire tree-huggers.
On the positive side, cruise control does free-up the driver's "brain" to concentrate on more important things like phone use, texting, reading important papers, eating a full meal, changing a top, etc etc